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avcodec/fate-idct8x8: Defined behavior: eliminate negative left-shifts.
The original code left-shifts negative values, which is undefined in the C99 specification (the one used during normal FFmpeg compilation). This change multiplies by (1 << shift), which is functionally equivalent, but has defined behavior. With this change, fate-idct8x8 compiled with --fsanitize=undefined works. Bug-Id: 686 Signed-off-by: Michael Niedermayer <michaelni@gmx.at> The assembly generated by gcc is unchanged by this commit
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@ -216,8 +216,8 @@ static av_always_inline void FUNC(row_fdct)(int16_t *data)
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tmp11 = tmp1 + tmp2;
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tmp12 = tmp1 - tmp2;
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dataptr[0] = (int16_t) ((tmp10 + tmp11) << PASS1_BITS);
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dataptr[4] = (int16_t) ((tmp10 - tmp11) << PASS1_BITS);
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dataptr[0] = (int16_t) ((tmp10 + tmp11) * (1 << PASS1_BITS));
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dataptr[4] = (int16_t) ((tmp10 - tmp11) * (1 << PASS1_BITS));
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z1 = MULTIPLY(tmp12 + tmp13, FIX_0_541196100);
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dataptr[2] = (int16_t) DESCALE(z1 + MULTIPLY(tmp13, FIX_0_765366865),
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@ -249,8 +249,8 @@ void ff_j_rev_dct(DCTBLOCK data)
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/* AC terms all zero */
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if (d0) {
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/* Compute a 32 bit value to assign. */
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int16_t dcval = (int16_t) (d0 << PASS1_BITS);
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register int v = (dcval & 0xffff) | ((dcval << 16) & 0xffff0000);
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int16_t dcval = (int16_t) (d0 * (1 << PASS1_BITS));
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register int v = (dcval & 0xffff) | ((dcval * (1 << 16)) & 0xffff0000);
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idataptr[0] = v;
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idataptr[1] = v;
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@ -272,8 +272,8 @@ void ff_j_rev_dct(DCTBLOCK data)
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tmp2 = z1 + MULTIPLY(-d6, FIX_1_847759065);
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tmp3 = z1 + MULTIPLY(d2, FIX_0_765366865);
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tmp0 = (d0 + d4) << CONST_BITS;
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tmp1 = (d0 - d4) << CONST_BITS;
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tmp0 = (d0 + d4) * CONST_SCALE;
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tmp1 = (d0 - d4) * CONST_SCALE;
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tmp10 = tmp0 + tmp3;
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tmp13 = tmp0 - tmp3;
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@ -284,8 +284,8 @@ void ff_j_rev_dct(DCTBLOCK data)
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tmp2 = MULTIPLY(-d6, FIX_1_306562965);
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tmp3 = MULTIPLY(d6, FIX_0_541196100);
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tmp0 = (d0 + d4) << CONST_BITS;
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tmp1 = (d0 - d4) << CONST_BITS;
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tmp0 = (d0 + d4) * CONST_SCALE;
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tmp1 = (d0 - d4) * CONST_SCALE;
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tmp10 = tmp0 + tmp3;
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tmp13 = tmp0 - tmp3;
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@ -298,8 +298,8 @@ void ff_j_rev_dct(DCTBLOCK data)
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tmp2 = MULTIPLY(d2, FIX_0_541196100);
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tmp3 = MULTIPLY(d2, FIX_1_306562965);
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tmp0 = (d0 + d4) << CONST_BITS;
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tmp1 = (d0 - d4) << CONST_BITS;
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tmp0 = (d0 + d4) * CONST_SCALE;
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tmp1 = (d0 - d4) * CONST_SCALE;
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tmp10 = tmp0 + tmp3;
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tmp13 = tmp0 - tmp3;
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@ -307,8 +307,8 @@ void ff_j_rev_dct(DCTBLOCK data)
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tmp12 = tmp1 - tmp2;
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} else {
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/* d0 != 0, d2 == 0, d4 != 0, d6 == 0 */
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tmp10 = tmp13 = (d0 + d4) << CONST_BITS;
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tmp11 = tmp12 = (d0 - d4) << CONST_BITS;
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tmp10 = tmp13 = (d0 + d4) * CONST_SCALE;
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tmp11 = tmp12 = (d0 - d4) * CONST_SCALE;
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}
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}
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@ -618,8 +618,8 @@ void ff_j_rev_dct(DCTBLOCK data)
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tmp2 = z1 + MULTIPLY(-d6, FIX_1_847759065);
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tmp3 = z1 + MULTIPLY(d2, FIX_0_765366865);
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tmp0 = (d0 + d4) << CONST_BITS;
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tmp1 = (d0 - d4) << CONST_BITS;
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tmp0 = (d0 + d4) * CONST_SCALE;
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tmp1 = (d0 - d4) * CONST_SCALE;
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tmp10 = tmp0 + tmp3;
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tmp13 = tmp0 - tmp3;
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@ -630,8 +630,8 @@ void ff_j_rev_dct(DCTBLOCK data)
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tmp2 = MULTIPLY(-d6, FIX_1_306562965);
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tmp3 = MULTIPLY(d6, FIX_0_541196100);
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tmp0 = (d0 + d4) << CONST_BITS;
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tmp1 = (d0 - d4) << CONST_BITS;
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tmp0 = (d0 + d4) * CONST_SCALE;
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tmp1 = (d0 - d4) * CONST_SCALE;
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tmp10 = tmp0 + tmp3;
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tmp13 = tmp0 - tmp3;
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@ -644,8 +644,8 @@ void ff_j_rev_dct(DCTBLOCK data)
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tmp2 = MULTIPLY(d2, FIX_0_541196100);
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tmp3 = MULTIPLY(d2, FIX_1_306562965);
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tmp0 = (d0 + d4) << CONST_BITS;
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tmp1 = (d0 - d4) << CONST_BITS;
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tmp0 = (d0 + d4) * CONST_SCALE;
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tmp1 = (d0 - d4) * CONST_SCALE;
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tmp10 = tmp0 + tmp3;
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tmp13 = tmp0 - tmp3;
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@ -653,8 +653,8 @@ void ff_j_rev_dct(DCTBLOCK data)
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tmp12 = tmp1 - tmp2;
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} else {
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/* d0 != 0, d2 == 0, d4 != 0, d6 == 0 */
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tmp10 = tmp13 = (d0 + d4) << CONST_BITS;
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tmp11 = tmp12 = (d0 - d4) << CONST_BITS;
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tmp10 = tmp13 = (d0 + d4) * CONST_SCALE;
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tmp11 = tmp12 = (d0 - d4) * CONST_SCALE;
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}
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}
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@ -110,12 +110,12 @@ static inline void FUNC(idctRowCondDC)(int16_t *row, int extra_shift)
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if (((((uint64_t *)row)[0] & ~ROW0_MASK) | ((uint64_t *)row)[1]) == 0) {
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uint64_t temp;
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if (DC_SHIFT - extra_shift >= 0) {
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temp = (row[0] << (DC_SHIFT - extra_shift)) & 0xffff;
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temp = (row[0] * (1 << (DC_SHIFT - extra_shift))) & 0xffff;
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} else {
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temp = ((row[0] + (1<<(extra_shift - DC_SHIFT-1))) >> (extra_shift - DC_SHIFT)) & 0xffff;
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}
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temp += temp << 16;
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temp += temp << 32;
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temp += temp * (1 << 16);
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temp += temp * ((uint64_t) 1 << 32);
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((uint64_t *)row)[0] = temp;
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((uint64_t *)row)[1] = temp;
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return;
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@ -127,11 +127,11 @@ static inline void FUNC(idctRowCondDC)(int16_t *row, int extra_shift)
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row[1])) {
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uint32_t temp;
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if (DC_SHIFT - extra_shift >= 0) {
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temp = (row[0] << (DC_SHIFT - extra_shift)) & 0xffff;
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temp = (row[0] * (1 << (DC_SHIFT - extra_shift))) & 0xffff;
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} else {
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temp = ((row[0] + (1<<(extra_shift - DC_SHIFT-1))) >> (extra_shift - DC_SHIFT)) & 0xffff;
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}
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temp += temp << 16;
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temp += temp * (1 << 16);
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((uint32_t*)row)[0]=((uint32_t*)row)[1] =
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((uint32_t*)row)[2]=((uint32_t*)row)[3] = temp;
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return;
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